Electrical circuitry often must be protected from disruptions caused by electromagnetic interference (EMI) and radio frequency interference (RFI) entering the system.
In addition to protecting electronic equipment against EMI/RFI energy, there is also a need to protect the equipment against power surges owing to electrostatic discharges (ESD) and electromagnetic pulse (EMP). The high voltage generated by ESD and EMP can damage voltage sensitive integrated circuits and the like.
Frequently today's electronic circuitry requires the use of high density, multiple contact electrical connectors. There are many applications in which it is desirable to provide a connector with a filtering capability, for example, to suppress EMI and RFI. In addition, there is often a need for a cost effective means of retrofitting existing electronic equipment to include filtering capability. To retain the convenience and flexibility of the connector, however, it is desirable that the filtering capability be incorporated into connectors in a manner that will permit full interchangeability between the connectors and their unfiltered counterparts. In particular, any filtered connector should in many instances retain substantially the same dimensions as the unfiltered version and should have the same contact arrangement so that either the filtered or the unfiltered version can be connected to an appropriate mating connector. Additionally it is sometimes desirable to filter only certain lines within a connector and to use the same basic connector in a number of applications, each requiring different selected lines to be filtered.
One means to protect against undesirable interference without altering the internal structure of a connector is by the use of shielding. The shielding may take several forms. For adequate protection, it is essential, however, that there be no break in continuity of the shielding.
Other means for shielding include the use of internal filtering arrangement that include the use of filter sleeves and planar filter members. Both of these methods generally require the additional space within the connector housing to accommodate the sleeves or other filtering devices. Furthermore, connectors of this type often include a number of labor intensive steps during the manufacture of the connectors. These connectors are not readily manufacturable by automatic equipment.
In many instances it is desirable to have an external filtering device that is an "add-on" device to provide filtering to an already existing non-filtered connector. This is particularly desirable in instances when the same basic connector may be used in a number of different applications, each requiring filtering of different lines in the connector. U.S. Pat. No. 4,804,332, owned by this assignee discloses a filtered electrical device adapted to be mounted externally to an electrical article such as an electrical connector and electrically engageable to circuit paths thereof. The device includes contact portions that are electrically engageable to corresponding contact sections of the electrical article. In some applications, it is desirable to have a means for filtering articles such as cable harness assemblies, for example, wherein the filtering device must be completely contained within the connectors used in the assembly. often the configuration of the connectors associated with such harnesses are of the type that is unsuitable for use with an externally mounted device. It is desirable, however, that an "add-on" filtering means be available for use with cable connectors.